The field of this invention relates to rust inhibitors for fuels and oils, particularly that photo-adducts of dimethylmaleic anhydride with olefins function effectively as rust inhibitors for fuels and oils.
It is an object of this invention to provide photo-adducts of dimethylmaleic anhydride with olefins as rust inhibitors for hydrogen fuels, such as gasoline, kerosene, etc., and oils. Another object is to provide novel compositions of matter. Further objects and advantages will become apparent as the description of the invention proceeds.
We have discovered novel rust inhibitors for liquid hydrocarbon fuels and oils. These rust inhibitors are photo-adducts of dimethylmaleic anhydride with olefins. The prior art has not recognized that photo-adducts of dimethyl maleic anhydride with olefins are useful as rust inhibitors for fuels and oils.
An article by G. O. Schenck, W. Hartman, and R. Steinmetz in Chem. BER. 96, 498 (1963) discloses the preparation of certain olefin photo-adducts with dimethylmaleic anhydride using a high-pressure arc as a source of ultra violet light. However, the prior art never contemplated the use of these compounds as rust inhibitors for fuels and oils; also certain novel compositions of matter are prepared by our novel process.
We have discovered that the photo-adducts of dimethylmaleic anhydride with olefins are effective rust inhibitors for fuels and oils. The olefins have the following structure: ##STR1## wherein R.sub.1 through R.sub.4 are the same or different alkyl or aralkyl groups containing 1 to 30 carbon atoms. Alternatively, one R group is an alkyl or aralkyl group and the other three R groups are hydrogen. If desired the R groups are suitably linked, as in cycloalkylolefins.
It is preferred to make the rust inhibitors for fuels and oils utilizing terminal olefins containing 8 to 30 carbon atoms.
Our novel rust inhibitors are effective with any hydrocarbon fuels, such as gasoline or kerosene or oil. Representative oils include automotive oils, railway diesel oils, turbine oils, and cutting oils. Our novel rust inhibitors are particularly effective rust inhibitors in concentrations of about 10 to 10,000 parts per million.
According to our novel process, dimethylmaleic anhydride forms photo-adducts with olefins when irradiated in solution in the presence of a sensitizer such as benzophenone, acetophenone, acetone, Rose Bengal, or methylene blue. The products are derivatives of cyclobutane. The following novel compositions useful as rust inhibitors for hydrocarbon fuels and oils were prepared utilizing our novel process: ##STR2## 1,2-dimethyl-3-n-hexylcyclobutane-1,2-dicarboxylic anhydride ##STR3##
The following examples illustrate the preferred embodiments of this invention. It will be understood that these examples are for illustrative purposes only and do not purport to be wholly definitive with respect to conditions or scope of the invention.